Business Segment's Contribution to Select Statements of Income (Loss) Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Policy charge revenue	$ 37,454	$ 38,242	$ 112,299	$ 113,141
Net investment income	27,427	29,224	81,788	83,290
Net realized investment gains (losses)	4,711	1,690	6,926	1,613
Derivative gains (losses)	(9,239)	(34,133)	(40,007)	(37,427)
Total Revenues	60,353	35,023	161,006	160,617
Interest credited to policyholder liabilities	13,207	13,637	39,560	41,620
Policy benefits (net of reinsurance recoveries)	(963)	(5,767)	1,436	59,146
Amortization (accretion) of DAC	1,139	1,995	2,876	2,437
Amortization (accretion) of VOBA	11,295	14,018	16,513	27,009
Insurance, general and administrative expenses	9,739	8,131	25,159	28,299
Total Benefits and Expenses	34,417	32,014	85,544	158,511
Income (Loss) Before Taxes	25,936	3,009	75,462	2,106
Income Tax Expense (Benefit)	0	0	575	0
Net Income (Loss)	25,936	3,009	74,887	2,106
Operating Segments | Annuity
Segment Reporting Information [Line Items]
Policy charge revenue	23,954	24,610	71,904	72,523
Net investment income	13,741	15,014	40,994	40,517
Net realized investment gains (losses)	3,558	200	5,247	1,030
Derivative gains (losses)	(9,239)	(34,272)	(40,007)	(37,587)
Total Revenues	32,014	5,552	78,138	76,483
Interest credited to policyholder liabilities	2,140	2,098	5,673	6,524
Policy benefits (net of reinsurance recoveries)	(9,261)	(18,819)	(21,441)	22,736
Amortization (accretion) of DAC	1,139	1,995	2,876	2,437
Amortization (accretion) of VOBA	1,011	1,358	3,246	4,447
Insurance, general and administrative expenses	9,041	7,762	22,937	26,168
Total Benefits and Expenses	4,070	(5,606)	13,291	62,312
Income (Loss) Before Taxes	27,944	11,158	64,847	14,171
Income Tax Expense (Benefit)	0	3,808	393	6,409
Net Income (Loss)	27,944	7,350	64,454	7,762
Operating Segments | Life Insurance
Segment Reporting Information [Line Items]
Policy charge revenue	13,500	13,632	40,395	40,618
Net investment income	13,686	14,210	40,794	42,773
Net realized investment gains (losses)	1,153	1,490	1,679	583
Derivative gains (losses)	0	139	0	160
Total Revenues	28,339	29,471	82,868	84,134
Interest credited to policyholder liabilities	11,067	11,539	33,887	35,096
Policy benefits (net of reinsurance recoveries)	8,298	13,053	22,877	36,411
Amortization (accretion) of DAC	0	0	0	0
Amortization (accretion) of VOBA	10,284	12,660	13,267	22,562
Insurance, general and administrative expenses	698	368	2,222	2,130
Total Benefits and Expenses	30,347	37,620	72,253	96,199
Income (Loss) Before Taxes	(2,008)	(8,149)	10,615	(12,065)
Income Tax Expense (Benefit)	0	(3,808)	182	(6,409)
Net Income (Loss)	$ (2,008)	$ (4,341)	$ 10,433	$ (5,656)